Cellular and wireless communication devices have seen explosive growth over the past several years. This growth has been fueled by better communications hardware, larger networks, and more reliable protocols. Today's smartphones include cameras, Global Positioning System (GPS) receivers, Bluetooth® transceivers, and of course the cellular communication capabilities (e.g., Long Term Evolution (LTE), 3G and/or 4G network access) to enable the mobile communication devices to establish data communication links with the Internet. Smartphones are now very widely deployed in society. Additionally, the components and capabilities in smartphones are now very affordable, enabling the capabilities to be deployed in other types of devices.
Many networks have been deployed to support these mobile communication devices. A wireless network may be distributed over land areas called cells. Each cell typically includes a base station or other access point that is capable of providing voice and/or data services to mobile communication devices having a subscription to that network. Each cell is generally surrounded by a number of neighbor cells. A mobile communication device selects and establishes a connection with a local cell as the serving cell for making and receiving voice calls on the wireless network subscription. The mobile communication device may periodically monitor the neighbor cells to determine whether there is a better cell available for making and receiving calls on the wireless network subscription. If so, the mobile communication device may reselect the serving cell to be the best available neighbor cell.
Mobile communication devices may include one or more network interfaces for accessing one or more respective network subscriptions. For example, a mobile communication device may be configured with a single subscriber identity module (SIM) card or multiple SIM cards that access or share access to a receiver/transmitter chain (i.e., the circuitry associated with the radio between the antenna and the modem). A mobile communication device may operate the network supporting one or more subscriptions in one of several modes, including an “active” mode and an “idle” mode. The mobile communication device generally performs neighbor cell monitoring on idle network subscriptions.
For example, a conventional single SIM mobile communication device operating in idle mode periodically “wakes up” and enables power to the receiver and other components to listen for paging messages over the paging channel of the idle subscription's serving cell. During this wake up period, the single SIM device also monitors neighbor cells that surround the current serving cell. As described, the single SIM device monitors neighbor cells to determine whether there is a better neighbor cell available for making and receiving calls on a network subscription. If so, the single SIM device may reselect the serving cell to be the best available neighbor cell. For example, in Global System for Mobile Communications (GSM) networks, the single SIM device may be aware of 32 neighbor cells that surround the serving cell of an idle network subscription. Neighbor cell monitoring may include the single SIM device monitoring the transmit signal power of the neighbor cells to determine the top neighbor cells, typically the top six. Neighbor cell monitoring may also include decoding certain control channels of the top neighbor cells, such as Synchronization Channel (SCH), Frequency Correction Channel (FCCH), and Broadcast Control Channel (BCCH) of a GSM network. By decoding such control channels of the top neighbor cells in advance, the single SIM device may identify and synchronize to a neighbor cell more quickly during a reselection. Once wake up processing is complete, the single SIM device may reenter a low power state and wait until the next wake up time. Such conventional monitoring of neighbor cells, however, reduces the standby time of the mobile device and consumes a significant amount of power.
In another example, a mobile communication device may be configured with two or more SIM cards sharing a single receiver/transceiver chain (e.g., a dual SIM dual standby “DSDS”). In such multi-SIM multi-standby (MSMS) devices, the receiver/transmitter chain tunes to a single network subscription one at a time, and therefore the two or more SIM interfaces cannot operate simultaneously. Thus, a MSMS device may monitor multiple interfaces in an idle mode by tuning to one network subscription and then to another network subscription. For example, the radio may connect to a first network subscription and periodically tune away to other idle network subscriptions to maintain service with those networks. The time that the mobile device tunes away from the first subscription to the idle subscription is typically aligned with the wake up time of the idle subscription. In this way, the conventional tune away procedure allows a MSMS device to listen for pages and perform neighbor cell monitoring on idle subscriptions. However, tuning away to an idle subscription typically interrupts data transmissions to and from an active subscription. Therefore, in MSMS devices, conventional monitoring of neighbor cells can reduce throughput of data transmitted to and received from the active network subscription. Such reduced throughput may be due to the mobile communication device pausing data communication on the active subscription for the duration that the MSMS device is tuned away to the idle network subscription.